The present disclosure relates to a method of processing a material layer, and particularly to a method of stripping an antireflective coating (ARC) layer from a substrate.
Photolithography is a process used in micro fabrication to selectively remove parts of a thin film or the bulk of a substrate. Photolithography uses light to transfer a geometric pattern from a photo mask to a light-sensitive photoresist, or simply “resist,” on the substrate. A series of chemical treatments then engrave the exposure pattern into the material underneath the photoresist. Typically, for negative tone development (NTD) the portion of the resist which has not been exposed to light is removed by an organic solvent during the development process, the most commonly used solvents are 2-heptanone and n-butyl acetate (NBA).
A strong demand exists for techniques that extend application of ArF immersion lithography. Besides techniques such as litho-friendly design, dual exposure/patterning schemes, customized illumination, alternative processing schemes are also viable candidates. One of the most promising alternative flows is to use image reversal by means of NTD. Traditionally, contact and trench printing use a dark-field mask in combination with positive tone resist and positive tone development (PTD). With NTD, the same features are printed in positive resist using bright-field masks, and consequently better image contrasts are provided.
An integrated process is needed to achieve this image contrast, before the final pattern is engraved, an organic planarization layer (OPL) is applied on top of the substrate, then a silicon-containing antireflective coating (SiARC) material designed for NTD application is coated to provide etch resistance and reflectivity control, and finally, an photoresist material is applied to provide the initial image transfer to the substrate. However, new challenges come with the introduction of NTD SiARC, especially the wet strip process was used to remove the NTD SiARC from Si monitor wafers. Many SiARC materials cannot be removed completely during this wet strip process using the common process flows used in the manufacture.